Conventionally, as means for decreasing the amount of electric charges in objects requiring electricity removal close to zero, there has been known an ionizer wherein high direct current or alternating current voltage from a high voltage generating unit is applied to a needle electrode and corona discharge is generated, and positive or negative ions are output by the needle electrode, and these ions are blown on charged objects with an air stream.
Further, for convenience in using the ionizer, there has also been known an ionizer structure wherein a hollow casing to contain a high voltage power unit and a control unit therein is arranged, and along the longitudinal direction of the casing, a plurality of electrode units each having a needle electrode for generating corona discharge are arranged in a line. (For example, refer to Japanese Unexamined Patent Application Publication No. 2002-260821).
In the case when an ionizer is structured as one contained in such a hollow casing as above, because it is necessary to make air flow around the needle electrode and thereby make generated ions flow in the direction of charged objects, an air flow path from a supply source for generating the air flow is opened around the needle electrode, and for this purpose, as shown in the Patent JP 2002-260821, it is usual to form the air flow path by joining upper and lower flat plate shaped flow route forming members that are joined with each other, wherein the portion for supporting the needle electrode in the air flow path is formed as a sleeve or the like.
However, in this case, the air flow path is formed by joining the upper and lower plate shaped flow route forming members whose areas are relatively large, and so, the force applied onto the corresponding flow route forming members becomes extremely large owing to air pressure that is supplied to the inside, therefore, the members cannot endure the inside air pressure unless their joining strength is increased sufficiently, and as a consequence, there are conditions that the flow route forming members must be formed large enough to have high strength, or the air pressure to be supplied must be lowered.
Further, because the flow route forming members are made separately from the hollow casing, they must be connected to the outside via a part of the hollow casing, and so for this reason, complicated assembly work such as connections with tubes or the like are required.